Method and apparatus for magnetic-optical printing

ABSTRACT

A method and apparatus for magnetic-optical printing employing a light-transparent uniformly magnetized magnetic medium upon which characters to be printed are first imaged magnetically and then delineated by optical masking using ferromagnetic toner, after which the characters are photographically recorded.

United States Patent Inventors Edward W. James, II

Oxford. Pm; Eustathios Vassiliou, Wilmington, Del. Appl. No 886,619 IFiled Dec. 19, 1969 Patented Sept. 14, 1971 Assignee E. I. du Pont deNemours and Company Wilmington, Del.

METHOD AND APPARATUS FOR MAGNETIC- OPTICAL PRINTING 10 Claims, 12Drawing Figs.

0.5. CI sis/4.5, 355/17 Int. Cl B4lb 13/00, 603g 19/00 Field of Search355/3, 17; 95/45; 346/74 References Cited UNITED STATES PATENTS2,954,006 9/ I960 Lawrence Primary Examiner-John M. Horan Anomey-HarryJ. McCauley ABSTRACT: A method and apparatus for magnetic-opticalprinting employing a light-transparent uniformly magnetized magneticmedium upon which characters to be printed are first imaged magneticallyand then delineated by optical masking using ferromagnetic toner, afterwhich the characters are photographically recorded.

PATENTEDSEPMIHTI 3,604,326

SHEET 1 [1F 5 JNVENTUHS 4 7 v Euslaill os vassiliou.

ATTORNEY Edward M. Jamagfl PATENTEUSEPMIS?! 3.604.326

' sum 2 or 5 a M I .50 I 38 a g I ATTORNEY METHOD AND APPARATUS FORMAGNETIC-OPTICAL PRINTING BRIEF SUMMARY OF THE INVENTION Generally, thisinvention comprises a method and apparatus for magnetic-optical printingutilizing a photographic recording medium which is exposed to a lightsource, comprising, in

sequence:

l. forming a magnetic pattern imaging the subject matter to be printedupon a light-transparent uniformly magnetized magnetic medium comprisinga light-transparent support carrying distributed particulate magneticmaterial affixed to the side of the support to be employed as therecording surface by characteristic magnetization of the particulatemagnetic material constituting the image of the subject matter to beprinted to a condition of different receptivity for ferromagnetic toneras contrasted with the adjacent background of the magnetic medium,

2. decorating the recording surface of the magnetic medium with aferromagnetic toner defining an adherent optical mask of the image,

. interposing the magnetic medium carrying the adherent optical mask ofthe image between the photographic recording medium and the associatedlight source, and

4. actuating the light source to emit exposure radiation through theoptical mask onto the photographic recording medium.

DRAWINGS FIG. 1 is a schematic fragmentary plan view of a representativemagnetic film which can be employed in the practice of this inventioncomprising a polymeric support film embossed on the recording surface toretain regularly spaced striations 'of binder in which are dispersedmagnetic particles, the asreceived magnetic condition being indicated byequal-length aligned magnetic vectors,

FIG. 2 is a schematic top plan view of a preferred embodiment ofapparatus constructed according to this invention, photographicsynchronization means being omitted,

FIG. 3 is a schematic perspective side view of the erase station of FIG.2,

FIG. 4 is a schematic partially broken perspective view of a preferreddesign of monosymbol magnetic imaging pole piece taken on line 4-4, FIG.2,

FIG. 5 is a schematic fragmentary plan view of the magnetic film of FIG.1 indicating the region of magnetization produced by a typical magneticimaging,

FIG. ,6. is.asecuormuiewtakeupnline 1 16.13 G.- AQflh toner decorateapparatus,

FIG. 7 is a fragmentary plan view of the magnetic film of FIGS. I and 5showing the lay down of an optical mask as a result of toner decoration,

FIG. 8 is a side elevation view of the photographic recording stationtaken on line 8-8, FIG. 2,

FIG. 9 is a schematic representation of a preferred apparatus forsequence control of the recording operation of the apparatus of FIG. 2,

FIG. 10 is a schematic representation of a single recognition AND gatein circuit connection with a single shift register making up the arrayof FIG. 9,

FIG. 11 is a schematic representation of a line margin confirmationapparatus provided for the synchronization of photographic recordingwith information receipt for the apparatus of FIG. 2, and

FIG. 12 is a schematic representation of a second embodiment ofapparatus for sequence control of the recording operation of theapparatus of FIG. 2.

Magnetic-optical printing according to this invention involvessequentially forming an invisible magnetic image of the subject matterto be printed on a light-transparent magnetic medium, rendering themagnetic image visible by laying down an adherent optical mask whichprecisely delineates the subject matter to be printed, and thereafterphotographically recording.

The magnetic medium employed in our method must thus be capable offorming clean-cut magnetic images of the subject matter to be printed,which can be of the size scale, typically, of pica typewriter charactersor the like, and subsequently permit sharp photographic readout throughthe agency of optical masking faithfully delineating the magneticimages.

A wide variety of magnetic recording films or plates can be made upwhich are satisfactory for our purposes, the general requirements ofwhich will become apparent from the detailed specifications of one typeof magnetic film with which applicants have had extensive experience.

This particular magnetic film is the subject matter of application Ser.No. 834,121, filed June 17, 1969, of common as signment herewith, whichcan typically comprise a flexible ultraviolet radiation-transmittingpolymeric tape, e.g., polycarbonate, polyvinyl chloride, celluloseacetate, or the like having a thickness of 0.1 to 10 mils. This tape isembossed on its recording surface to provide recesses into whichlight-opaque particulate magnetic material is loaded as a suspension ina settable binder, such as Aroplaz" or the like as hereinafterdescribed, which permits uniform magnetic orientation of the magneticmaterial particles without agglomeration prior to anchoring in placeupon set up of the binder. The embossing pattern employed is such as togive a regular distribution of the particulate magnetic materialemployed, which thus displays very uniform magnetic behavior over thefull film expanse and yet possesses an overall light transmissionranging from about 5 percent to about percent, preferably at least 50percent for the purposes of this invention. As hereinafter described, itis preferred to use ultraviolet radiation for the particularphotographic recording employed as an example, and, thus, the film, inthis instance, should transmit ultraviolet light. However, conventionalphotography using visible light is an equally feasible alternative, inwhich case a magnetic medium transparent to visible light is, of course,necessary.

The particulate magnetic material in this instance was relativelymagnetically hard, in that it consisted of very finely divided chromiumdioxide (00 in either substantially pure state or modified with otherreactive elements. The preferred particle size was about 1 micronmaximum dimensionor under, although some particles measuring about 10microns can be used and, of course, there was a tendency for particlesto agglomerate, so that agglomerations frequently attained 10 micronseffective size. In the particle size employed, the magnetic material hadboth a relatively high coercivity and remanence, which was desirable foradherent optical mask formation as hereinafter described. Suitablechromium dioxide-containing compositions are detailed in U.S. PATS. Nos.2,956,955, 3,117,093, 3,074,778, 3,078,147, 3,278,263, 2,923,683-4,3,034,988, 3,068,176 and 2,923,685. The compositions described in thesepatents relate to magnetic materials having relatively low Curietemperatures; however, this property is not employed in the preferredpractice of our invention, although the magnetic imaging step of ourinvention can be accomplished using this property if desired.

It is essential that there exist substantially uniform opticaltransparency and, at the same time, the maintenance of strong enoughmagnetic fields between spaced magnetic particles or their agglomeratesto attract magnetic toner particles uniformly independent of the extentof the magnetized area. While these properties are to some degreemutually opposed, a compromise which is entirely satisfactory consistsin spacing magnetic patterns (e.g. lines, dots, combinations of each, orother configurations) about one-fiftieth inch to one fifteenhundredthinch apart (i.e., 50 to 1500 lines/in.) and preferably one-fiftieth inchto one five-hundredth inch apart (i.e., 50 to 500 lines/in.). The depththe magnetic stratum consisting of binder loaded with uniformlydispersed particulate magnetic solids was limited to from 0.05 to 2mils, and preferably from 0.1 to 1 mil.

ln a typical instance, acicular chromium dioxide particles having themagnetic properties iH =465 oersteds, a,=80.5 emu/g. aF38.2 emu/g. werethoroughly dispersed by ink milling with an alkyd binder (e.g., Aroplaz1271, a long oil linseed alkyd marketed by Archer-Daniels-Midland Co.)and Stoddard solvent. During the milling the paste produced was diluted,as necessary, by adding the Stoddard solvent, and was further dilutedwith the same solvent to give a paste of about 600 poises viscosity attime of use. At this point the ratio of Cro /alkyd/stoddard solvent was66/22/12 percent by weight. The weight ratio of CrO to binder was 3:1.

The resulting paste was doctored into embossed line or groove recessesof a Lexan (polycarbonate resin marketed by the General Electric Co.)film support to give a smooth recording surface, after which themagnetic particles were given a common horizontal orientation coplanarwith the support film surface and transverse to the grooves by passingthe freshly coated film between the opposing poles of two closely spacedU-shaped magnets, four passes through a field of 10,000 gauss giving80-85 percent orientation (i.e., alignment of the c-axis, orneedle-axis, of the particles perpendicular to the edges of the groovesin the plane of the film as determined by magnetometer techniques). Thealkyd binder was then allowed to harden at room temperature over night,thereby locking the magnetic particles in the preferred direction of themagnetization. After hardening, any excess CrO- and binder were removedfrom the lands between the grooves by abrading the surface of the filmwith 0.5 micron A1 slurried in water to give the desired opticaltransparency.

A typical film provided with a line pattern is shown in FIG. 1, whereinthe coparallel striations of the light-transparent support film 11 werefilled with particulate O0 dispersed in binder so as to defineindividual bands about 0.8 mil wide spaced about 1.2 mil apart, underwhich conditions the film is 0 approximately 60 percent open (i.e.,substantially light-transparent). At this size scale, the bands werevirtually invisible to the unaided eye, although they were, in fact,light-opaque, due to their suspended magnetic particle content.Nevertheless, the support film still presented 60 percentlight-transparent residual area, which was entirely adequate for thefinal photographic recording step of this invention. The magnetic stateobtained by the common horizontal magnetic orientation coplanar with thesupport film is denoted schematically by the equal length magneticvectors drawn transversely of bands 10.

The mechanical arrangement of a preferred embodiment of apparatusaccording to this invention is detailed schematically in plan in FIG. 2,and utilizes an endless flexible belt form magnetic film medium 14 whichcan have the striated regular line pattern of FIG. 1.

Belt 14 is trained around two sheaves, with its recording surfacedisposed in a vertical plane outwardly thereof, sheave 15 being drivenin successive equal angular steps by stepper motor 16 whereas sheave 17is an idler. The direction of belt travel is generally clockwise, asseen in FIG. 2, so that belt 14 travels sequentially past I) an erasestation 19, (2) a write state 20, (3) a decorate station 21, (4) aphotographic recording station 22 and (5) a cleanup station 23, afterwhich the cycle repeats.

As shown in FIG. 3, wherein the film line pattern is omitted, the erasestation comprises essentially a strong permanent magnet 25 having a flatpole face disposed in close proximity to the recording surface oftraveling belt 14. The film arriving at the erase station has itsmagnetic particle loading in a state of unique characteristicmagnetization as a result of preceding magnetic imaging and cleanupoperations, and this is denoted by the broken arrow pairs signifyingwhat is effectively the demagnetized state, as hereinafter described ingreater detail with respect to write station 20. The polarity of magnet25 and its magnetizing strength are preselected to restore the magneticmedium to its uniform magnetized condition depicted in FIG. 1.

Upon leaving the erase station, belt 14 advances stepwise as impelled bystepper motor 16, until it is brought before write station 20.Preferably, writing is accomplished by monosymbol units, although thedot matrix or line synthesis methods taught in Gleason PAT. 2,841,461can be utilized equally well, if desired.

A single monosymbol write element, specifically that for the smallletter e", is detailed in FIG. 4, it being understood that write station20 comprises a multiplicity of monosymbol write elements (typically 64in number) arranged side-by-side on 0.1" centers in a line lengthwise ofbelt 14 along which it is desired to imprint characters.

The design of monosymbol write element detailed in FIG. 4 comprises acore 28 made up of a multiplicity of soft iron laminations, in order toreduce eddy currents, to the end of which is attached the molded ferriteclip 29 carrying the integral individual type font character 30. Thus,each character 30 is a shaped pole piece defining a single alphabeticletter, numeral or other symbol. The type font characters are disposednormal to belt 14, which is indexed to the right as indicated by thearrow in FIG. 4, in close adjacency to the belt recording surface, butout of contact therewith.

The magnetic flux circuit through the belt is completed via a laminatedferromagnetic yoke 36 underlying core 28 having one upstanding facedisposed in close proximity to the side of belt 14 opposite character 30and the other upstanding end in contact with the inboard end of core 28.The magnetic flux gap at the film passage point is 5 mils or less.

Magnetizing coil 31 is wrapped around core 28 with one end connected to.a driving amplifier 32, hereinafter described in greater detail, and theother end grounded at 33. Magnetic imaging is effected by an electricpulse transmitted while belt 14 is at rest within write station 20between successive steps in its advance. The pulse produces a magneticfield emanating from the pole face constituting the upraised characteron type font 30, thereby effectively demagnetizing belt 14 in themagnetic particle-loaded area immediately opposite the character. Thisoccurs as a result of momentary magnetization in the hard direction ofthe CrO particles, that is, normal to the caxis. However, when the fieldis removed by decay of the pulse, the Q0 particles immediately revert totheir original caxis magnetization, except that, statistically, one halfend up with a polarization to the left and one half to the right. Thus,the projected monosymbol region is effectively demagnetized, a uniquecondition denoted by the broken arrow pairs reversed in direction ashereinbefore mentioned with reference to FIG. 3. This forms a magneticimage of the letter e of the type font 30 as represented schematicallyby the alteration of the magnetic vector field of FIG. 1 to that shownin FIG. 5, the region of unique magnetization being bounded by fulllines whereas the remainder of the letter, impinging on the transparentintervening open spaces, is shown in broken line representation. i

It will be understood that a grossly disproportionate size scale wasutilized in drawing FIG. 5 in order to better portray the directionalconventions of the magnetization vectors. The magnetic images of thesymbols to be recorded are actually much larger in proportion to thewidths of striations 10 as well as the spacings therebetween, the smallletter e, in typewriter pica style, for example, spanning fortystriations 10 together with their intervening spacings.

Belt 14 next passes around idler sheave 17 to decorate station 21 whereit is dusted with fine magnetic powder toner (typically a mixture of 10micron diameter particles containing Fe+ F4230 dispersed in a carnaubawax binder).

A preferred design of decorate station is that detailed in FIG. 6, whichutilizes a pair of counter rotating permanent magnet rolls, 40 and 41,carrying on their surfaces a plurality of dipoles (not shown). Theserolls are preferably encased in rubber sleeves provided to reduce themagnetic field at the surfaces to a level appreciably below that havingany effect on belt 14 while still retaining a strength attracting tonerparticles to the roll peripheries. Rolls 40 and 41 are journaled withinhousing 42, provided with hinged cover 43, with shaft centers invertical alignment, roll 41 being topmost.

A fractional horsepower motor, not shown, which can also simultaneouslydrive a small screw conveyor returning toner particles from cleanupstation 23 to decorate station 21, preferably drives roll 40, achain-sprocket connection from the latter (not shown) being then used todrive roll 41.

Housing 42 is a reservoir for toner particles 44, which are retained inthe lower one third thereof to a depth covering approximately the lowerhalf of roll 40, which attracts the particles to its periphery in thecourse of rotation, thereby building up a thickness of, typically 0.1"of transported particles on the rubber sleeve surface. Roll 41, drivenat close clearance (typically 0.05") from roll 40, magneticallytransfers toner particles to its own periphery and carries them aroundto about 2 o'clock position where a nonmagnetic doctor blade 45 scrapesthem off continuously. The toner drops from the lower end of doctorblade 45 as an even stream falling onto the recording surface of belt14, advanced at an inclination of about 60 with the horizontal throughaligned slots 46 cut in the end walls of housing 42, thereby laying downthe optical mask, such as 38, FIG. 7. Excess toner slides off the loweredge of belt 14 and returns to the accumulation 44.

FIG. 7 is intended to represent the magnetic image after optical maskingin true scale with respect to the widths of the striations 10 and theirintervening transparent spacings, i.e., an expanse of approximately 40striations spanning the full width of the example letter e. Mask 38 isformed by the magnetic fields of the vectors within striations 10extended areawise by induced magnetization through toner particle ropesor chains which cover the entire area surrounding demagnetized zoneswith a light-opaque covering of toner particles which, collectively,define the optical mask. It will be understood that the demagnetized CrOparticles attract only very small amounts of toner, so that theobscuring effect contributed thereby is limited to the internal area ofstriations 10 where there is no interference with optical maskinganyway. Also, in demagnetization, the dipole structure is effectivelydestroyed, so that ropes or chains of obscuring toner particles are notformed within the regions where not desired. Mask 38 is quite adherentand clings to belt 14 without dislodgement by gravity or start and stopshocks during the succession of steps advancing the belt to thephotorecording station 22.

Photorecording station 22, FIG. 8, comprises a linear photographicexposure lamp 50, such as an E. G. & G. Co. xenon type FX-lC-9, providedwith an appropriate filter, not shown, disposed adjacent the decoratedface of belt 14. Photographic contact printing is employed wherein thebelt is isolated from the photographic recording paper 51, which cantypically be ultraviolet radiation-sensitive Type 503 DyluxQ, byprovision of a thin ultraviolet radiation-transparent membrane 52therebetween barring passage of toner particles constituting part ofoptical mask 38. (It is sometimes advantageous to substitute a specialfiber-optic window for membrane 52 in order to prevent light diffusionreducing the sharpness of optical masking.) Flash lamp 50 is operatedintermittently as hereinafter described to record characters imaged onbelt 14 in line-by-line sequence, after which photographic recordingpaper 51 is indexed vertically a distance presenting fresh paper forprinting the next-succeeding line by conventional paper advance rolls 53not detailed further. It should be mentioned that recording on paper 51is effectuated by light exposure solely, no subsequent development stepsbeing required, so that visual recording of information is complete withthe light exposure.

The next station in order is cleanup station 23 at which the tonerparticles constituting the optical mask on belt 14 are strippedtherefrom by an electromagnet 55 disposed in close proximity thereto butout of contact with the surface. The coil 55a of this electromagnet isenergized with AC current to produce a field pattern of sufficientintensity to disengage all toner particles from the belt.

The toner particles drop into the hopper of a screw conveyor, or onto abelt or other suitable transport means, indicated generally at 56, andare returned to toner sump 44 at decorate station 21. The clean belt 14then clears drive sheave l5 and once again arrives at erase station 19when the entire cycle hereinbefore described is repeated.

The operation of this invention is time-asynchronous, in that inputinformation is processed as received, after which the apparatus remainsinactive but in readiness for any elapsed time until a subsequent inputis received.

A preferred apparatus for the sequence control of recording is the shiftregister combination shown in FIG. 9. Here the information input isintroduced in binary code serially as electric pulses via line 59, itbeing understood that the source can be conventional, e.g. selectiveswitch readout from a perforated tape, the electric pulse transmissionof a communication line or in other usual manner. In accordance withconventional practice, the input from line 59 is of two general kinds:(1) informational and, therefore, of a type to be recorded by theapparatus of this invention, and (2) control, e.g. word spacing,carriage return, line spacing and the like which is not to be recorded.It will be understood that stepper motor 16 is provided with controlcircuitry well known to the art, and therefore not detailed herein,causing it to step upon the receipt of all inputs, both informationaland control, wherever required for the recording operation inconventional format.

Assuming, as an example, the use of an 8-bit code which, with 1 bitreserved to parity, leaves 7 bits to accommodate 2 or 128 individualcharacters, which is sufficient capacity for many uses, the infonnationinput can be through the 8-bit, 2 rank shift register, the first rank60aof which receives the input serially and, thereafter, upon receipt ofa strobe pulse through line 61, shifts its contents in parallel tosecond rank storage 60b. Reset of the second rank is effected by a resetpulse supplied through line 62 in proper time relationship with thestrobe pulse supplied the first rank. The information is then advancedin parallel, step-by-step as each reset pulse is received via line 62,through the 128 cell 7-bit shift registers shown in partial array at 64,the progress being horizontally from left to right from Register No. lto Register No. 128.

A plurality of individual symbol recognition AND gates 65 is providedbeneath array 64, the general circuit for 7 bit interrogation of eachindividual shift register n in turn being detailed in FIG. 10. All ANDgates 65 conduct their interrogations simultaneously when supplied witha strobe pulse via line 66 and, whenever the code identificationassigned to an individual symbol is found to exist across encodingconnections 65a (all shown open in FIG. 10 for purposes of generality)gate 65 transmits a voltage pulse through conventional driver amplifier32 and coil 31 (FIG. 4) to ground, thereby effecting magnetic imaging ofthe specific desired symbol on the appropriate point on belt 14.

Line-by-line photographic recording is conveniently effected by theapparatus schematically shown in FIG. 11.

As is customary in information handling, there is provided acharacteristic signal in the data input flow signalling the beginning ofeach line of input receipt.

One monosymbol magnetic imaging apparatus as detailed in FIG. 4 can bereserved for left-hand marginal verification of line arrival atphotorecording station 22. Preferably, the recording pole piece for thisdevice is disposed out of the regular line of character recording, FIG.11 showing the indicia as a magnetically imaged rectangular window 67located on belt 14 at a point below the line of informational imagingindicated by the word FAST defined by the optical mask 38'. Asindicated, window 67 has been demagnetized in the identical mannerhereinbefore described for symbol imaging generally, and has been maskedoptically at decorate station 21, so that it defines alight-transmitting area of, typically, 0.l" 0.1".

A continuously illuminated light source 68 on the rear side of belt 14is trained through a tube, not shown, in line with window 67 at theappropriate left-hand margin point within recording station 22 of FIG. 2at which photographic recording is to be effected. Then lighttransmission through window 67 activates photocell 69, which delivers anelectric current output to trigger switch 70 which, in tum, connectspower supply 71 in operative circuit with flash lamp 50, FIG. 8, therebytransmitting a flash of recording paper exposure radiation throughoptical mask 38'. It will be understood that window 67 is out of theline of sight of lamp 50 and paper 51, so that there is no photographicprintout of the window, which is solely an internal signal facility andnot of informational significance.

A second embodiment of time sequence control is representedschematically in FIG. 12 wherein belt 14 is effectively dividedlengthwise into two parallel tracks, the upper track, 14 of which isreserved exclusively for location coding, whereas the lower track, 14,,is reserved exclusively for information printin.

Here a magnetic write head 74 is provided in confrontation with therecording face of the magnetic belt to image magnetically in code 75 theas-received sequence of symbols to be printed responsive to theinformation input fed to the write head via line 73.

A sensor 76 is provided downline for each individual symbol to beprinted and a magnetic writing head 77, which can be of the same designas that shown in FIG. 4, corresponding to the same symbol as that forwhich an individual sensor 76 is reserved, is disposed in exacttransverse alignment therewith across the belt but in confrontation withthe information printin track 14,,

Sensors 76 can incorporate discriminatory AND gates such as thosehereinbefore described with reference to FIG. 10, enabling recognitionof the coded counterpart of each symbol in turn as the belt advancesfrom left to right, whereupon each sensor 76 actuates its associatedwriting head 77 via circuit connections not detailed when the beltarrives thereunder. The writing heads 77 then effect the magneticimaging of the information on the belt in the same manner ashereinbefore described.

With this embodiment it is understood that a common erase magnet 25 isemployed to simultaneously restore the magnetic condition of both tracks14,, and 14 to original state permitting reuse of the belt forrepetitive recording.

It will be understood that recording according to this invention, evenwith stepped belt operation, can be effected at relatively high speeds,it being practicable to pring approximately 4 lines/sec. wherein eachline consists of 70-80 characters.

If information input is at a constant fast rate, magnetic imaging can bedone on the fly, thereby dispensing with stepped operation. However,conventional light sources 50 emit their light over a perceptible timeperiod, which tends to smear" the photographic recording unless belt 14is halted at least long enough to effect line-by-line recording asdescribed. If a high speed light source is employed, the entireoperation can be on a continuous basis, without belt stopping except asdictated by the information input.

While flexible tape magnetic films of the design represented by belt 14are especially preferred in the practice of this invention because ofease of manipulation, low first cost and very long service light interms of multicyclic utilization, rigid plates of polymer, glass or awide variety of other materials are completely operative substitutes andmay, in particular circumstances, be actually preferred. Also, magneticfilm media in roll form, as distinguished from endless belts, can beemployed if desired. Roll type magnetic film has the advantage thatpermanent storage of magnetically imaged information is therebyafforded, with visual printout practicable at any optional subsequenttime. The magnetic particles utilized can have a wide variety ofcompositions as well as particulate orientations and dispositions, (r inthe orientations and striation and random loading patterns describedbeing only by way of examples. The photographic recording can beaccomplished by a wide variety of techniques, including the use ofconventional photographic film.

Characteristic demagnetization as described has proved effective inmagnetic imaging; however, it is also practicable if desired, to utilizeseveral cycles of damped AC voltage applied through coils 31.

Moreover, although black-on-white recording has been hereinbeforedescribed as preferred, white-on-black is equally convenientlyobtainable by merely reversing the characteristic magnetizations.

What is claimed is:

1. Apparatus for magnetic-optical printing comprising, in combination inthe following sequential operating order:

a. magnetic recording means forming a magnetic image of subject matterto be recorded upon a light-transparent magnetic medium comprising alight-transparent support carrying distributed particulate magneticmaterial affixed to the surface of said support reserved as the magneticrecording surface in a density preserving substantial opticaltransparency throughout said support,

b. decorate means dispensing magnetic toner on said recording surface ofsaid magnetic medium defining an adherent optical mask of said image,

c. a photographic recording medium-exposure light source subassemblyprovided with means for the interposition between said photographicrecording medium and said exposure light source of said magnetic mediumcarrying said adherent optical mask of said image, and

. means actuating said exposure light source to emit exposure radiationthrough said optical mask onto said photographic recording medium.

2. Apparatus for magnetic-optical printing according to claim 1 whereinsaid photographic recording medium-exposure light source subassembly isof a type such that the exposure radiation is primarily in theultraviolet range.

3. Apparatus for magnetic-optical printing according to claim 1responsive to sequential subject matter input provided with meanseffecting step-by-step sequential operation coordinated in sequence withreceipt of said subject matter input.

4. Apparatus for magnetic-optical printing according to claim 1 whereinsaid subject matter to be recorded is received as a sequentialelectrical pulse digital code information input to be printed upon saidmagnetic medium advanced linearly to accommodate said information inputspacewise provided, in series connection, with (1) a multirank shiftregister receiving said input in series sequence and (2) an array ofmultibit shift registers advancing said input in parallel, said multibitshift registers (2) being provided with individual symbol recognitiongates effecting selective formation of said magnetic image of saidsubject matter to be recorded in sequence corresponding to saidinformation input.

5. Apparatus for magnetic-optical printing according to claim 1 whereinsaid subject matter to be recorded is received as a sequentialelectrical pulse digital code information input to be printed upon saidmagnetic medium advanced linearly to accommodate said information inputspacewise provided, in series arrangement, with (1) magnetic write-inmeans recording said pulse code information input along a first track ofsaid magnetic medium reserved for information input receipt, (2)individual symbol recognition sensors disposed along said first trackdetecting the spaced arrival of individual items of said informationinput and (3) individual magnetic write-in means responsive to saidindividual symbol recognition sensors effecting selective formation ofsaid magnetic image of said subject matter to be recorded in sequencecorresponding to said information input along a second track of saidmagnetic medium reserved for said optical printing.

8. Apparatus for magnetic-optical printing according to claim 7 whereinsaid light-transparent magnetic-medium comprises an endless flexiblebelt.

9. Method for magnetic-optical printing utilizing a photographicrecording medium which is exposed to an associated light source,comprising, in sequence:

a. forming a magnetic pattern imaging the subject matter to be printedupon a light-transparent uniformly magnetized magnetic medium comprisinga light-transparent support carrying distributed particulate magneticmaterial affixed to the surface of said support reserved as the magneticrecording surface by characteristic magnetization of said particulatemagnetic material constituting the image of said subject matter to beprinted to a condition of different receptivity for ferromagnetic toneras contrasted with the adjacent background of said magnetic medium,

b. decorating said recording surface of said magnetic medium with aferromagnetic toner defining an adherent optical mask of said image,

c. interposing said magnetic medium carrying said adherent optical maskof said image between said photographic recording medium and saidassociated light source, and

d. actuating said light source to emit exposure radiation through saidoptical mask onto said photographic record ing medium.

10. A method for magnetic-optical printing according to claim 9 whereinthe step (d) of said printing is effected using ultraviolet radiation.

1. Apparatus for magnetic-optical printing comprising, in combination inthe following sequential operating order: a. magnetic recording meansforming a magnetic image of subject matter to be recorded upon alight-transparent magnetic medium comprising a light-transparent supportcarrying distributed particulate magnetic material affixed to thesurface of said support reserved as the magnetic recording surface in adensity preserving substantial optical transparency throughout saidsupport, b. decorate means dispensing magnetic toner on said recordingsurface of said magnetic medium defining an adherent optical mask ofsaid image, c. a photographic recording medium-exposure light sourcesubassembly provided with means for the interposition between saidphotographic recording medium and said exposure light source of saidmaGnetic medium carrying said adherent optical mask of said image, andd. means actuating said exposure light source to emit exposure radiationthrough said optical mask onto said photographic recording medium. 2.Apparatus for magnetic-optical printing according to claim 1 whereinsaid photographic recording medium-exposure light source subassembly isof a type such that the exposure radiation is primarily in theultraviolet range.
 3. Apparatus for magnetic-optical printing accordingto claim 1 responsive to sequential subject matter input provided withmeans effecting step-by-step sequential operation coordinated insequence with receipt of said subject matter input.
 4. Apparatus formagnetic-optical printing according to claim 1 wherein said subjectmatter to be recorded is received as a sequential electrical pulsedigital code information input to be printed upon said magnetic mediumadvanced linearly to accommodate said information input spacewiseprovided, in series connection, with (1) a multirank shift registerreceiving said input in series sequence and (2) an array of multibitshift registers advancing said input in parallel, said multibit shiftregisters (2) being provided with individual symbol recognition gateseffecting selective formation of said magnetic image of said subjectmatter to be recorded in sequence corresponding to said informationinput.
 5. Apparatus for magnetic-optical printing according to claim 1wherein said subject matter to be recorded is received as a sequentialelectrical pulse digital code information input to be printed upon saidmagnetic medium advanced linearly to accommodate said information inputspacewise provided, in series arrangement, with (1) magnetic write-inmeans recording said pulse code information input along a first track ofsaid magnetic medium reserved for information input receipt, (2)individual symbol recognition sensors disposed along said first trackdetecting the spaced arrival of individual items of said informationinput and (3) individual magnetic write-in means responsive to saidindividual symbol recognition sensors effecting selective formation ofsaid magnetic image of said subject matter to be recorded in sequencecorresponding to said information input along a second track of saidmagnetic medium reserved for said optical printing.
 6. Apparatus formagnetic-optical printing according to claim 3 provided in sequenceafter said photographic recording medium-exposure light sourcesubassembly with electromagnetic means stripping said magnetic tonerfrom said light-transparent magnetic medium.
 7. Apparatus formagnetic-optical printing according to claim 6 provided in sequenceafter said electromagnetic means stripping said magnetic toner from saidlight-transparent magnetic medium with magnetic erase means restoringsaid light-transparent magnetic medium to uniform magnetized conditionsuitable for subsequent magnetic reimaging utilization.
 8. Apparatus formagnetic-optical printing according to claim 7 wherein saidlight-transparent magnetic medium comprises an endless flexible belt. 9.Method for magnetic-optical printing utilizing a photographic recordingmedium which is exposed to an associated light source, comprising, insequence: a. forming a magnetic pattern imaging the subject matter to beprinted upon a light-transparent uniformly magnetized magnetic mediumcomprising a light-transparent support carrying distributed particulatemagnetic material affixed to the surface of said support reserved as themagnetic recording surface by characteristic magnetization of saidparticulate magnetic material constituting the image of said subjectmatter to be printed to a condition of different receptivity forferromagnetic toner as contrasted with the adjacent background of saidmagnetic medium, b. decorating said recording surface of said magneticmedium with a ferromagnetic toner defining an adherent optical mask ofsaid image, c. interposing said magnetic medium carrYing said adherentoptical mask of said image between said photographic recording mediumand said associated light source, and d. actuating said light source toemit exposure radiation through said optical mask onto said photographicrecording medium.
 10. A method for magnetic-optical printing accordingto claim 9 wherein the step (d) of said printing is effected usingultraviolet radiation.